Pigs without Slurry Smell (2014-2016)

During earlier research it has been found that fresh slurry, out of a slurry tray with frequent collection, contains almost 4 times as many biogas as slurry of 120 days old out of a traditional slurry cellar. In a slurry tray there is less fermentation than in a traditional cellar. The slurry trays also give less emission of ammonia and other gasses. Click here for the report of this research (in Dutch). To achieve this, frequent removal of the slurry must be possible. In 2013 they investigated this at VIC Sterksel. During this research they found out that a good removal of slurry within 3 days is very well possible when using shallow slurry trays in a channel with a width of 200cm. They also looked at the differences between composite slats and concrete slats. Click here for a report of this reserach (in Dutch).

To develope one or more systems with which we can get the slurry out of the stable quicker, at the end of 2014 we started the project "Pigs without Slurry Smell". This was a project that lasted 1,5 year, during which we wanted to develope a few new innovations. All innovations were aimed at getting slurry out of the stable as fast as possible and thus lower/minimalise the emissions out of the pit as fas as possible.

The first innovation is using a super hydrofobe coating (nanotechnology) on slurry trays, slats and separating walls in the pens. This coating makes a little contact surface, which causes fluids to "jump off" the surface. This means, for example, that slurry doesn't dry in and gets stuck on the surface and that it is easier to get it out of the stable. When the pens stay clean, the pigs also stay cleaner and that reduces the formation of dust. The question was if the coating alone is enough to remove the slurry as fast as possible. Maybe it could be combined with a slurry slidesystem or a spiral or screw system.

With the slurry slide we wanted to push the slurry to the drainage point in the slurry gutter. The slide didn't had to take alle the slurry with it in one take. It can go up and down several times, so the slurry stays in motion quitely, which prevents the slurry from drying in and getting stuck on the surface of the gutter. In 2015 we tested this principle in our warehous and after that we placed a prototype in a stable, so we could test it in real life. From the observations and experiences during these tests, we could conclude that the system works, but that it's very expansive to maintain and that service costs will also be very high, because of the location of the slide below the slats. Therefore we decided not to pursue this idea any further.The spiral/screw system makes sure the slurry in the pit is being mixed constantly, so it can't dry in. Besides that, this system makes sure that the slurry can be removed regulary. During this research it became clear that this system also works, but that it is very vulnerable for wear and tear and malfunction. Beacause of the place of the system below the slats, the costs for maintanance and service will become so high that they outweigh the benefits. So therefore we also decided not to pursue this idea any further. However, we will continue our research for similar systems which are less sensitive and easier to maintain.

Before this project we already developed two other ways to reduce the emission of ammonia in the pit and to remove the slurry out of the stable fast, namely the polyester gutter with cooling and our vacuum+ system. During this project we wanted to optimize these sytems further.During the test with the slurry tray with cooling we found out that the temperature at the top of the tray was much higher than at the bottom. At the bottom of the trays the temperature can be brought down to 14°C, but at the top of the tray the temperature wouldn't get lower than 20°C. Bringing down the temperature even further, will cost to much energy compared to the benefits. That's why we've decided not to pursue this any further and to start focus on getting the slurry out of the stable faster.

The vacuum+ system has been installed in a pig stable and a test setup has been placed at a cattle farm. At he cattle farm several tests have been done with different kinds of slurry and these were very promising. To develop this system further a new research project has been requested and this request was granted. During this new project we want to install the system in a complete stable with cattle.